Define Absorption, Storage and Elimination of ascorbic acid?
Ascorbic acid is rapidly absorbed from the intestines primarily by active transport. Simple diffusion or carrier-mediated transport may also contribute to a small extent of uptake of the vitamin from the mouth and stomach. Prior to absorption, ascorbate may be oxidized to form dehydroascorbate which is absorbed by passive diffusion or by use of glucose transporters. It passes through the portal vein to the general circulation and to all tissues. Each organ or tissue has an optimal saturation level of ascorbic acid. It is not stored to any appreciable extent in the body. The degree of absorption decreases with increased vitamin intake and varies from 16% to 98%, the average overall absorption being about 80% to 95%. Unabsorbed vitamin C may be metabolized by the intestinal flora. Pectin and zinc are a few substances that impair its absorption. Excess is excreted in urine.